Linear block copolymer composition

ABSTRACT

To provide a block copolymer composition excellent in balance of transparency, impact resistance, etc. in the form of not only an excluded product and a blow molded product but also an injection molded product. A linear block copolymer composition having at least three types of polymer blocks with different molecular weights each comprising a vinyl aromatic hydrocarbon as monomer units, wherein the molecular weight distribution of a mixture of the polymer blocks is within a specific range, and in GPC of the mixture, M1/M2 is within a specific range, where M1 is the peak top molecular weight corresponding to a peak at which the peak top molecular weight becomes maximum among peaks forming a proportion of the area of at least 30% to the whole peak area, and M2 is the peak top molecular weight corresponding to a peak at which the peak top molecular weight becomes minimum among peaks at which the peak top molecular weight is at most 50,000 and which form a proportion of the area of at least 20% to the whole peak area.

TECHNICAL FIELD

The present invention relates to a novel linear block copolymercomposition comprising a vinyl aromatic hydrocarbon and a conjugateddiene. Particularly, it relates to a linear block copolymer compositionexcellent in transparency and impact resistance and useful as it is oras a blending agent with various thermoplastic resins.

BACKGROUND ART

A block copolymer comprising a vinyl aromatic hydrocarbon and aconjugated diene and having a relatively high content of the vinylaromatic hydrocarbon is widely used for an application to injectionmolding or for an application to extrusion, such as sheets and films, byvirtue of its excellent characteristics such as transparency and impactresistance. Particularly, some such block copolymers and styrene polymercompositions having such a block copolymer blended therewith, which areexcellent in transparency, impact resistance, etc., have been proposed.

For example, JP-A-52-78260 discloses a linear copolymer compositionwherein the molecular weight distribution at a vinyl aromatichydrocarbon block moiety is from 2.3 to 4.5 and a branched blockcopolymer composition wherein the molecular weight distribution at avinyl aromatic hydrocarbon block moiety is from 2.8 to 3.5, which isproduced by blending. JP-B-2-59164 discloses a linear block copolymerand a branched block copolymer, wherein the molecular weightdistribution at a vinyl-substituted aromatic hydrocarbon block moiety isfrom 1.2 to 2.0. JP-A-53-286 discloses a branched block copolymerwherein the ratio of the number average molecular weight of a highmolecular weight component to a low molecular weight component at avinyl-substituted aromatic hydrocarbon block moiety in two linearcopolymers prior to coupling is from 3 to 7, and its production process.JP-A-7-173232 discloses a branched block copolymer having at least threepolymer blocks each comprising a vinyl aromatic hydrocarbon as monomerunits, and its production process. Further, JP-A-57-28150 discloses amethod of combining a branched block copolymer wherein the molecularweight distribution at a vinyl aromatic hydrocarbon block moiety is outof the range of from 2.8 to 3.5.

However, such block copolymers and compositions of such a blockcopolymer with a thermoplastic resin formed by the above methods arepoor in balance of transparency, impact resistance, etc. Particularly ininjection molding, molding is carried out under a high shearing force,whereby a molded product is likely to have anisotropy and tends to bepoor in strength in a certain direction, and a sufficient molded productcan hardly be provided.

DISCLOSURE OF THE INVENTION

Under these circumstances, the present inventors have conductedextensive studies to obtain a block copolymer composition excellent inbalance of transparency, impact resistance, etc. in the form of not onlyan extruded product and a blow molded product but also an injectionmolded product and as a result, found that the impact resistance isextremely improved without deteriorating transparency even in the formof an injection molded product by use of a linear block copolymercomposition comprising at least three polymer blocks with differentmolecular weights, each comprising a vinyl aromatic hydrocarbon asmonomer units, wherein the molecular weight distribution of a mixture ofthe polymer blocks is within a specific range, and in a gel permeationchromatogram of the mixture of the polymer blocks, M1/M2 is within aspecific range, where M1 is the peak top molecular weight correspondingto a peak at which the peak top molecular weight becomes maximum amongpeaks forming a proportion of the area of at least 30% to the whole peakarea, and M2 is the peak top molecular weight corresponding to a peak atwhich the peak top molecular weight becomes minimum among peaks at whichthe peak top molecular weight is at most 50,000 and which form aproportion of the area of at least 20% to the whole peak area. Thepresent invention has been accomplished on the basis of this discovery.

Namely, the present invention relates to a composition of a linear blockcopolymer comprising from 55 to 95 mass % of a vinyl aromatichydrocarbon and from 5 to 45 mass % of a conjugated diene as monomerunits based on the total mass of the copolymer, characterized in thatthe linear block copolymer is a mixture of a linear block copolymerhaving at least three polymer blocks with different molecular weights,each comprising a vinyl aromatic hydrocarbon as monomer units andrepresented by the following formula:S—B—S(wherein S is a polymer block comprising a vinyl aromatic hydrocarbon asmonomer units, and B is a polymer block comprising a conjugated diene asmonomer units) and further, (1) the molecular weight distribution of amixture of the polymer blocks each comprising a vinyl aromatichydrocarbon as monomer units, is within a range of from 3.35 to 6, and(2) in a gel permeation chromatogram of a mixture of the polymer blockseach comprising a vinyl aromatic hydrocarbon as monomer units, M1/M2 iswithin a range of from 12.5 to 25, where M1 is the peak top molecularweight corresponding to a peak at which the peak top molecular weightbecomes maximum among peaks forming a proportion of the area of at least30% to the whole peak area, and M2 is the peak top molecular weightcorresponding to a peak at which the peak top molecular weight becomesminimum among peaks at which the peak top molecular weight is at most50,000 and which form a proportion of the area of at least 20% to thewhole peak area.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a chromatogram obtained by measuring a linear block copolymercomposition under measurement conditions 2.

FIG. 2 is a chromatogram of a polymer content obtained by subjecting alinear block copolymer composition to ozonolysis and then reduction withlithium aluminum hydride.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, the present invention will be explained in detail below.

The vinyl aromatic hydrocarbon used for the linear block copolymercomposition of the present invention may, for example, be styrene,o-methylstyrene, p-methylstyrene, p-tert-butylstyrene,1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene orvinylanthracene, and styrene is particularly commonly mentioned. Theymay be used alone or as a mixture of two or more of them.

The conjugated diene is a diolefin having 4 or 8 carbon atoms and havinga pair of conjugated double bonds, and it may, for example, be1,3-butadiene, 2-methyl-1,3-butadiene (isoprene),2,3-dimethyl-1,3-butadiene, 1,3-pentadiene or 1,3-hexadiene.1,3-Butadiene or isoprene is particularly commonly mentioned. They maybe used alone or as a mixture of two or more of them.

The linear block copolymer composition of the present inventioncomprises from 55 to 95 mass % of a vinyl aromatic hydrocarbon and from5 to 45 mass % of a conjugated diene as monomer units, based on thetotal mass of the polymer. If the linear block copolymer compositioncomprises a vinyl aromatic hydrocarbon in an amount exceeding 95 mass %and a conjugated diene in an amount less than 5 mass % as monomer units,it tends to be poor in impact resistance. On the other hand, if thelinear block copolymer composition comprises a vinyl aromatichydrocarbon in an amount less than 55 mass % and a conjugated diene inan amount exceeding 45 mass % as monomer units, it tends to be poor intransparency, moldability, rigidity, heat stability, etc.

The linear block copolymer composition preferably comprises from 60 to85 mass % of a vinyl aromatic hydrocarbon and from 15 to 40 mass % of aconjugated diene as monomer units, based on the total mass of thepolymer, whereby it tends to have more favorable balance of impactresistance and transparency. Further, the linear block copolymercomposition more preferably comprises from 65 to 75 mass % of a vinylaromatic hydrocarbon and from 25 to 35 mass % of a conjugated diene asmonomer units, whereby it tends to have furthermore favorable balance ofphysical properties such as impact resistance, transparency andmoldability.

The linear block copolymer contained in the linear block copolymercomposition of the present invention is a mixture of a linear blockcopolymer having at least three polymer blocks with different molecularweights, each comprising a vinyl aromatic hydrocarbon as monomer units,represented by the following formula:S—B—S(wherein S is a polymer block comprising a vinyl aromatic hydrocarbon asmonomer units, and B is a polymer block comprising a conjugated diene asmonomer units).

Namely, the linear block copolymer composition comprises at least 3types, preferably from 3 to 6 types, more preferably 3 types, of polymerblocks each comprising a vinyl aromatic hydrocarbon as monomer units,whereby the linear block copolymer composition of the present inventionis very excellent in balance of physical properties such as impactresistance, transparency and moldability.

Further, as it comprises at least 3 types, preferably from 3 to 6 types,more preferably 3 types, of the polymer blocks, it has a favorablecompatibility with a styrene resin such as a polystyrene, andaccordingly a resin composition obtained by mixing such a blockcopolymer composition with a styrene resin tends to have favorablebalance of physical properties such as impact resistance, transparencyand moldability. As mentioned above, it is essential that the linearblock copolymer composition of the present invention comprises at leastthree polymer blocks each comprising a vinyl aromatic hydrocarbon asmonomer units.

Further, it is essential that the molecular weight distribution of amixture of the polymer blocks each comprising a vinyl aromatichydrocarbon as monomer units is within a range of from 3.35 to 6. Whenthe molecular weight distribution of the polymer block mixture is withinthis range, the compatibility of the polymer block mixture with astyrene resin such as a polystyrene will be favorable, whereby a resincomposition obtained by mixing such a linear block copolymer compositionwith a styrene resin tends to have very excellent impact resistance andtransparency. If the molecular weight distribution of such a polymerblock mixture is out of the range of from 3.35 to 6, a resin compositionobtained by mixing such a linear block copolymer composition with astyrene resin tends to have insufficient impact resistance andtransparency, and tends to be poor in moldability.

Among the linear block copolymer compositions of the present inventionwherein the molecular weight distribution of the polymer block mixtureis within a range of from 3.35 to 6, a linear block copolymercomposition wherein the molecular weight distribution is within a rangeof from 3.35 to 4.5 is more excellent in balance between transparencysuch as a total luminous transmittance or a haze and an area impactproperty as evaluated by a falling weight test or the like, ascharacteristics of the linear block copolymer composition as it is or aresin composition obtained by mixing such a linear block copolymercomposition with a styrene resin. On the other hand, a linear blockcopolymer composition wherein the molecular weight distribution iswithin a range of from 4.5 to 6 is slightly poor in transparency such asa total luminous transmittance or a haze, but is very excellent innotched impact resistance as evaluated by a Charpy impact test or thelike, as characteristics of the linear block copolymer composition as itis or a resin composition obtained by mixing such a linear blockcopolymer composition with a styrene resin. If the molecular weightdistribution is less than 3.35, the linear block copolymer compositionas it is or a resin composition obtained by mixing such a blockcopolymer composition with a styrene resin tends to be poor in impactresistance, and if it exceeds 6, a resin composition obtained by mixingsuch a block copolymer composition with a styrene resin tends to be poorin transparency. As mentioned above, the present invention ischaracterized in that materials having various characteristics can beobtained by properly controlling the molecular weight distribution ofthe polymer block mixture within a range of from 3.35 to 6.

Within the range of the molecular weight distribution of from 3.35 to4.5 within which the linear block copolymer composition will be moreexcellent in balance between transparency and impact resistance, themolecular weight distribution is more preferably within a range of from3.5 to 4.5, furthermore preferably from 3.5 to 4. On the other hand,within the range of the molecular weight distribution of from 4.5 to 6within which the linear block copolymer composition will be veryexcellent in notched impact resistance, the molecular weightdistribution is more preferably within a range of from 4.5 to 5.5,furthermore preferably from 4.5 to 5.

In order to batch off a mixture of polymer blocks S1, S2 and S3, eachcomprising a vinyl aromatic hydrocarbon as monomer units, a method maybe employed wherein a block copolymer mixture containing the linearblock copolymer is subjected to ozonolysis and then reduction withlithium aluminum hydride, and the resulting polymer content is obtained,as disclosed in Polymer, vol. 22, 1721 (1981), Rubber Chemistry andTechnology, vol. 59, 16 (1986), Macromolecules, vol. 16, 1925 (1983),etc.

As conditions for measuring the polymer block mixture thus batched offby gel permeation chromatography (GPC), a GPC column with a number oftheoretical plate of at least 32,000 is used.

More specifically, the following measurement conditions 1 may bementioned.

[Measurement Conditions 1]

Solvent (mobile phase): THF

Flow rate: 1.0 ml/min

Preset temperature: 40° C.

Column structure: One column of TSK guardcolumn MP (xL) 6.0 mmID×4.0 cmmanufactured by TOSOH CORPORATION and two columns of TSK-GEL MULTIPOREHXL-M 7.8 mmID×30.0 cm (number of theoretical plate: 16,000)manufactured by TOSOH CORPORATION, a total of three columns in the orderof TSK guardcolumn MP (xL), TSK-GEL MULTIPORE HXL-M and TSK-GELMULTIPORE HXL-M (number of theoretical plate: 32,000 as a whole)

Sample injection amount: 100 μL (sample liquid concentration 1 mg/ml)

Column pressure: 39 kg/cm²

Detector: RI detector

Further, it is essential for the linear block copolymer composition ofthe present invention that in a gel permeation chromatogram of themixture of the polymer blocks each comprising a vinyl aromatichydrocarbon as monomer units, M1/M2 is within a range of from 12.5 to25, where M1 is the peak top molecular weight corresponding to a peak atwhich the peak top molecular weight becomes maximum among peaks forminga proportion of the area of at least 30% to the whole peak area, and M2is the peak top molecular weight corresponding to a peak at which thepeak top molecular weight becomes minimum among peaks at which the peaktop molecular weight is at most 50,000 and which form a proportion ofthe area of at least 20% to the whole peak area. When M1/M2 is within arange of from 12.5 to 25, the linear block copolymer composition and amixed resin composition comprising it and a styrene resin tend to havemore improved impact resistance. M1/M2 is more preferably within a rangeof from 12.7 to 21.5, furthermore preferably from 13 to 20.

If M1/M2 is less than 12.5, the linear block copolymer composition as itis or a resin composition obtained by mixing such a linear blockcopolymer composition with a styrene resin tends to be poor in impactresistance, and if it exceeds 25, a resin composition obtained by mixingsuch a block copolymer composition with a styrene resin tends to be poorin transparency.

Further, in a gel permeation chromatogram of the mixture of the polymerblocks each comprising a vinyl aromatic hydrocarbon as monomer units,when M5/M2 is within a range of from 2 to 4, where M5 is the peak topmolecular weight of a component forming a proportion of the area of from3 to 15% to the whole peak area among peaks at which peak top molecularweight is from 13,000 to 50,000, the linear block copolymer compositionand a mixed resin composition comprising it and a styrene resin tend tohave more improved impact resistance. M5/M2 is more preferably within arange of from 2.2 to 3.6. If M5/M2 is less than 2, the linear blockcopolymer composition as it is or a resin composition obtained by mixingsuch a linear block copolymer composition with a styrene resin may bepoor in transparency in some cases, and if it exceeds 4, a resincomposition obtained by mixing such a block copolymer composition with astyrene resin may be poor in impact resistance in some cases.

The above peak top molecular weights M1, M2 and M5 can be obtained bymeans of GPC as follows. Namely, the peak top molecular weight of eachpeak component in the polymer block mixture can be obtained bycalculation in accordance with a known method (such as “Gel PermeationChromatography”, p. 81 to 85 (1976, published by Maruzen Company,Limited, Japan)) using a GPC curve prepared by subjecting the mixture ofthe polymer blocks each comprising a vinyl aromatic hydrocarbon asmonomer units to GPC and a calibration curve prepared from the peakcount and the molecular weight obtained by subjecting a monodispersedpolystyrene to GPC. Employing the proportion of the area of each peak,among peaks forming a proportion of the area of at least 30% to thewhole peak area, a peak at which the peak top molecular weight becomesmaximum is selected to obtain the peak top molecular weight M1 of acomponent to which the peak is attributable, and among peaks at whichthe peak top molecular weight is at most 50,000 and which form aproportion of the area of at least 20% to the whole peak area, a peak atwhich the peak top molecular weight becomes minimum is selected toobtain the peak top molecular weight M2 of a component to which the peakis attributable. Further, among peaks at which the peak top molecularweight is from 13,000 to 50,000, a peak forming a proportion of the areaof from 3 to 15% to the whole peak area is selected to obtain the peaktop molecular weight M5 of a component to which the peak isattributable. As measurement conditions of the polymer block mixture byGPC, it is preferred to use a GPC column with a number of theoreticalplate of at least 32,000.

More specifically, the measurement conditions 1 are employed, asexplained above for determination of the molecular weight distributionof the mixture of the polymer blocks each comprising a vinyl aromatichydrocarbon as monomer units.

In the gel permeation chromatogram of the mixture of the polymer blockseach comprising a vinyl aromatic hydrocarbon as monomer units, when theproportion of the number of moles of S1 to the sum of the numbers ofmoles of S1 and S2 is preferably within a range of from 5 to 25 mol %,where S1 is a component corresponding to a peak at which the peak topmolecular weight becomes maximum among peaks forming a proportion of thearea of at least 30% to the whole peak area, and S2 is a componentcorresponding to a peak at which the peak top molecular weight becomesminimum among peaks at which the peak top molecular weight is at most50,000 and which form a proportion of the area of at least 20% to thewhole peak area, the linear block copolymer composition and a mixedresin composition comprising it and a styrene resin tend to have afavorable balance of impact resistance, transparency and moldability.The proportion of the number of moles of S1 to the sum of the numbers ofmoles of S1 and S2 is particularly preferably within a range of from 6to 20 mol %, furthermore preferably from 6.5 to 17 mol %. If theproportion of the number of moles of S1 to the sum of the numbers ofmoles of S1 and S2 is less than 5 mol %, the linear block copolymercomposition and a mixed resin composition comprising it and a styreneresin tend to be poor in transparency, and if the proportion of thenumber of moles of S1 to the sum of the numbers of moles of S1 and S2exceeds 25 mol %, the linear block copolymer composition and a mixedresin composition comprising it and a styrene resin tend to be poor inimpact resistance.

The molar ratio of S1 and S2 can be calculated, in the present inventionfor example, as molar fractions from the values of M1 and M2 and thevalues of areas of the corresponding peaks on a chromatogram of amixture of S1 and S2 by GPC.

Further, in view of balance of impact resistance, transparency andmoldability of the linear block copolymer composition, in the gelpermeation chromatogram of the mixture of the polymer blocks eachcomprising a vinyl aromatic hydrocarbon as monomer units, the peak topmolecular weight corresponding to a peak at which the peak top molecularweight becomes maximum among peaks forming a proportion of the area ofat least 30% to the whole peak area is preferably from 90,000 to200,000, and the peak top molecular weight corresponding to a peak atwhich the peak top molecular weight becomes minimum among peaks at whichthe peak top molecular weight is at most 50,000 and which form aproportion of the area of at least 20% to the whole peak area ispreferably from 4,500 to 20,000.

Further, it is more preferred that the peak top molecular weightcorresponding to a peak at which the peak top molecular weight becomesmaximum among peaks forming a proportion of the area of at least 30% tothe whole peak area is from 100,000 to 170,000, and the peak topmolecular weight corresponding to a peak at which the peak top molecularweight becomes minimum among peaks at which the peak top molecularweight is at most 50,000 and which form a proportion of the area of atleast 20% to the whole peak area is from 5,000 to 10,000.

Further, the peak top molecular weight corresponding to a peak forming aproportion of the area of from 3 to 15% to the whole peak area amongpeaks at which the peak top molecular weight is from 13,000 to 50,000 ispreferably from 14,000 to 25,000 in view of balance of impactresistance, transparency and moldability of the linear block copolymercomposition, and the peak top molecular weight is more preferably from16,000 to 23,000.

In the linear block copolymer composition of the present invention, themolecular weight distribution of the component corresponding to a peakat which the peak top molecular weight becomes maximum among peaksforming a proportion of the area of at least 30% to the whole peak areais preferably less than 1.03, whereby a mixture containing such a linearblock copolymer composition tends to have more improved impactresistance, particularly area impact property. The molecular weightdistribution of the component corresponding to a peak at which the peaktop molecular weight becomes maximum among peaks forming a proportion ofthe area of at least 30% to the whole peak area is more preferablywithin a range of from 1.005 to 1.025.

The proportion of the area of the above peak to the whole peak area isobtained preferably by measurement using a GPC column with a number oftheoretical plate of at least 100,000 using a gel permeationchromatograph prepared by measuring the linear block copolymercomposition of the present invention by GPC and a calibration curveprepared by using a commercial standard polystyrene for GPC. Morespecifically, the following measurement conditions 2 may be mentioned,

[Measurement Conditions 2]

Solvent (mobile phase): THF

Flow rate: 0.2 ml/min

Preset temperature: 40° C.

Column structure: One column of KF-G 4.6 mmID×10 cm manufactured bySHOWA DENKO K.K. and four columns of KF-404HQ 4.6 mmID×25.0 cm (numberof theoretical plate: 25,000) manufactured by SHOWA DENKO K.K., a totalof five columns in the order of KF-G, KF-404HQ, KF-404HQ, KF-404-HQ andKF-404HQ (number of theoretical plate: 100,000 as a whole)

Sample injection amount: 10 μL (sample liquid concentration 2 mg/ml)

Column pressure: 127 kg/cm²

Detector: RI detector

Further, in the linear block copolymer composition of the presentinvention, M3/M4 is preferably within a range of from 2.5 to 4.5, whereM3 is the peak top molecular weight corresponding to a peak at which thepeak top molecular weight becomes maximum among peaks forming aproportion of the area of at least 30% to the whole peak area, and M4 isthe peak top molecular weight corresponding to a peak at which the peaktop molecular weight becomes minimum among peaks forming a proportion ofthe area of least 15% to the whole peak area. When M3/M4 is within arange of from 2.5 to 4.5, a mixed resin composition comprising such alinear block copolymer composition and a styrene resin tends to havemore improved impact resistance. M3/M4 is particularly preferably withina range of from 2.9 to 4. If M3/M4 is less than 2.5, the linear blockcopolymer composition and a mixed resin composition comprising it and astyrene resin tend to be poor in impact resistance, and if it exceeds4.5, the linear block copolymer composition and a mixed resincomposition comprising it and a styrene resin tend to be poor intransparency.

The peak top molecular weight M3 is determined by selecting a componentcorresponding to a peak at which the peak top molecular weight becomesmaximum among peaks forming a proportion of the area of at least 30% tothe whole peak area, and obtaining the peak top molecular weight of sucha component.

Similarly, the peak top molecular weight M4 is determined by selecting acomponent corresponding to a peak at which the peak top molecular weightbecomes minimum among peaks forming a proportion of the area of at least15% to the whole peak area, and obtaining the peak top molecular weightof such a component.

The peak top molecular weight of the linear block copolymer compositioncomprising a polymer block comprising a vinyl aromatic hydrocarbon asmonomer units and a polymer block comprising a conjugated diene asmonomer units can also be determined by GPC under the same conditionsfor the above-explained determination of the molecular weightdistribution of a component corresponding to a peak at which the peaktop molecular weight becomes maximum among peaks forming a proportion ofthe area of at least 30% to the whole peak area. Namely, M3 and M4 arevalues as calculated as PS. Further, as a specific example of conditionsfor measuring the copolymer by GPC, the above-described measurementconditions 2 may be mentioned.

In the linear block copolymer composition of the present invention, thepeak top molecular weight of a component providing a maximum peak areain a gel permeation chromatogram is preferably within a range of from120,000 to 250,000, more preferably from 140,000 to 220,000, furthermorepreferably from 150,000 to 200,000. Particularly when the peak topmolecular weight of a component providing a maximum peak area in a gelpermeation chromatogram is less than 120,000, the linear block copolymercomposition and a mixed resin composition comprising it and a styreneresin tend to be poor in impact resistance, transparency andmoldability, and if it exceeds 250,000, the linear block copolymercomposition and a mixed resin composition comprising it and a styreneresin tend to be poor in transparency and moldability.

In order to obtain a gel permeation chromatogram of the linear blockcopolymer composition, it is preferred to use a GPC column with a numberof theoretical plate of at least 100,000. More specifically, theabove-described measurement conditions 2 may be mentioned.

As an organic solvent to be used for production of the linear blockcopolymer composition of the present invention, a known organic solventsuch as an aliphatic hydrocarbon such as butane, pentane, hexane,isopentane, heptane, octane or isooctane, an alicyclic hydrocarbon suchas cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane orethylcyclohexane, or an aromatic hydrocarbon such as benzene, toluene,ethylbenzene or xylene may be used.

Further, an organic lithium compound is a compound having at least onelithium atom bonded to its molecule, and for example, ethyllithium,n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium ort-butyllithium may be used.

In production of the linear block copolymer composition of the presentinvention, a small amount of a polar compound may be dissolved in asolvent. The polar compound is used to improve efficiency of aninitiator, to adjust the microstructure of a conjugated diene, or as arandomizing agent in a case where a vinyl aromatic hydrocarbon and aconjugated diene are copolymerized. The polar compound to be used forproduction of the linear block copolymer composition of the presentinvention may, for example, be an ether such as tetrahydrofuran,diethylene glycol dimethyl ether or diethylene glycol dibutyl ether, anamine such as triethylamine or tetramethylethylenediamine, a thioether,a phosphine, a phosphoramide, an alkylbenzene sulfonate, or an alkoxideof potassium or sodium. A preferred polar compound is tetrahydrofuran.

The polymerization temperature in production of the linear blockcopolymer composition of the present invention is usually from −10° C.to 150° C., preferably from 40° C. to 120° C. The time required forpolymerization varies depending upon the conditions, but is usuallywithin 48 hours, particularly preferably from 0.5 to 10 hours. Further,the atmosphere in the polymerization system is preferably replaced withan inert gas such as a nitrogen gas. The polymerization pressure is notparticularly limited so long as the polymerization is carried out undera pressure sufficient to maintain monomers and a solvent in a liquidphase within the above polymerization temperature range. Further, it isnecessary to pay attention not to incorporate impurities whichinactivate an initiator and a living polymer, such as water, oxygen orcarbon dioxide gas into the polymerization system.

After completion of the polymerization, a substance having activehydrogen such as water, an alcohol, carbon dioxide, an organic acid oran inorganic acid as a polymerization terminator is added forinactivation in an amount sufficient to inactivate active terminals. Atthis time, when water or an alcohol is used as the polymerizationterminator for example, hydrogen is introduced to a polymer chainterminal, and when carbon dioxide is used, a carboxyl group isintroduced. Accordingly, by appropriately selecting the polymerizationterminator, linear block copolymer compositions containing blockcopolymer components having various functional groups on their terminalscan be produced.

The mixture of a linear block copolymer having at least 3 types ofblocks each comprising a vinyl aromatic hydrocarbon as monomer units,represented by the following formula:S—B—Sof the present invention can be obtained, for example, by the followingmethod (1), (2) or (3).

(1) It can be obtained by blending linear block copolymers of the aboveformula produced by a conventional living anionic polymerization methodusing an organic lithium compound as an initiator in a hydrocarbonsolvent within a range as defined in the present invention. Otherwise,it can be obtained by the following methods.

(2) First, a vinyl aromatic hydrocarbon is subjected to anionicpolymerization using an initiator, and then successive addition of aninitiator and a vinyl aromatic hydrocarbon to the polymerization systemis carried out twice, to form a polymer block comprising three types ofvinyl aromatic hydrocarbons with different peak top molecular weights asmonomer units. Then, a conjugated diene is added and further, successiveaddition of a vinyl aromatic hydrocarbon is carried out, and then allactive terminals of the polymer are inactivated to obtain a polymerwithin a range as defined in the present invention.

(3) First, a vinyl aromatic hydrocarbon is subjected to anionicpolymerization using an initiator, and then successive addition of aninitiator and a vinyl aromatic hydrocarbon to the polymerization systemis carried out twice, to form a polymer block comprising three types ofvinyl aromatic hydrocarbons with different peak top molecular weights asmonomer units. Then, a conjugated diene is added and further, successiveaddition of a vinyl aromatic hydrocarbon is carried out, and then partof active terminals of the polymer are inactivated, the polymerizationis continued, and then a vinyl aromatic hydrocarbon is further added, toobtain a polymer within a range as defined in the present invention.

Now, a method for producing the linear block copolymer composition bythe above method (2) or (3) will be explained in further detail below.

As a first stage polymerization, a block comprising a vinyl aromatichydrocarbon as monomer units is polymerized. For this polymerization, acharge amount is determined so as to obtain an aimed molecular weight,and then a vinyl aromatic hydrocarbon, an organic lithium compoundinitiator, a solvent and as the case requires, a polar compound aredissolved, and the polymerization is carried out at a predeterminedtemperature. The amount of the solvent charged is, as the ratio of thecharge amount of the solvent to the total monomer amount, is preferablysuch that the solvent/total monomer amount is from 20/1 to 2/1 (weightratio), more preferably from 10/1 to 2.5/1 (weight ratio). If thesolvent/total monomer amount is at least 20/1, the productivity tends tobe poor, and if the solvent/total monomer amount is at most 2/1, theviscosity of the polymer liquid tends to increase, which may impair thereaction. As the ratio of charge amount of the solvent to the polarcompound, the polar compound/solvent is preferably from 1/100,000 to1/1,000 (weight ratio), more preferably from 1/10,000 to 1/3,333 (weightratio). If the polar compound/solvent is less than 1/100,000, theefficiency of the initiator tends to be poor, and if the polarcompound/solvent exceeds 1/1,000, the microstructure of the conjugateddiene may be impaired, whereby the impact resistance tends to be poor.

As the ratio of the charge amount of the first stage organic lithiumcompound initiator to the total monomer amount, the first stage organiclithium compound initiator/total monomer amount is preferably from1/4,000 to 1/6,000 (weight ratio), more preferably from 1/4,400 to1/5,600 (weight ratio). As the ratio of the total monomer amount to thecharge amount of the first stage vinyl aromatic hydrocarbon, the totalmonomer amount/first stage vinyl aromatic hydrocarbon is preferably from2/1 to 4/1 (weight ratio), more preferably from 2.5/1 to 3.5/1 (weightratio). Further, as the ratio of the total organic lithium compoundinitiator amount to the charge amount of the first stage organic lithiumcompound initiator, the total organic lithium compound initiator/firststage organic lithium compound initiator is preferably from 3 to 10(molar ratio), more preferably from 4 to 7 (molar ratio). Completecompletion of the first stage polymerization reaction is taken as theend point of the polymerization. It is preferred that after completionof the first stage polymerization reaction, predetermined amounts of anorganic lithium compound initiator and a vinyl aromatic hydrocarbon arenewly added to the polymerization system to initiate a second stagepolymerization. The end point of the polymerization can be judged bymeasuring the solid content concentration in a sampled polymer liquid toconfirm whether or not a polymer at a predetermined concentration isformed. Otherwise, it may be judged by confirming that substantially nounreacted monomer remains by e.g. gas chromatography.

With respect to the amounts of the organic lithium compound initiatorand the vinyl aromatic hydrocarbon added for the second stagepolymerization, their charge amounts are determined to obtain aimedmolecular weights with respect to a polymer chain continuously preparedfrom living polymer active terminals formed in the first stagepolymerization and a polymer chain prepared from the organic lithiumcompound initiator newly added at the completion of the first stagepolymerization.

As the ratio of the charge amount of the second stage organic lithiumcompound initiator to the total monomer amount, the second stage organiclithium compound initiator/total monomer amount is preferably from1/1,400 to 1/11,000 (weight ratio), more preferably from 1/2,500 to1/9,000 (weight ratio). As the ratio of the total organic lithiumcompound initiator amount to the charge amount of the second organiclithium compound initiator, the organic lithium compoundinitiator/second stage organic lithium compound initiator is preferablyfrom 1.5/1 to 12/1 (molar ratio), more preferably from 2.5/1 to 10.5/1(molar ratio).

Further, as the ratio of the total monomer amount to the charge amountof the second vinyl aromatic hydrocarbon, the total monomeramount/second stage vinyl aromatic hydrocarbon is preferably from 9.5/1to 25/1 (weight ratio), more preferably from 11/1 to 24/1 (weightratio). The vinyl aromatic hydrocarbon is added and polymerization iscontinued at a predetermined temperature, and complete completion of thepolymerization reaction is taken as the end point of the second stagepolymerization. It is preferred that after completion of the secondstage polymerization, predetermined amounts of an organic lithiumcompound initiator and a vinyl aromatic hydrocarbon are newly added tothe polymerization system to initiate a third stage polymerization. Theend point of the polymerization can be judged by measuring the solidcontent concentration in a sampled polymer liquid to confirm whether ornot a polymer at a predetermined concentration is formed. Otherwise, itmay be judged by confirming that substantially no unreacted monomerremains by e.g. gas chromatography.

With respect to the amounts of the organic lithium compound initiatorand the vinyl aromatic hydrocarbon added in the third stagepolymerization, their charge amounts are determined to obtain aimedmolecular weights with respect to a polymer chain prepared continuouslyfrom the living polymer active terminals formed in the first and secondstage polymerization and a polymer chain prepared from the organiclithium compound initiator newly added at the completion of the secondstage polymerization. As the ratio of the charge amount of the thirdstage organic lithium compound initiator to the total monomer amount,the third stage organic lithium compound initiator/total monomer amountis preferably from 1/1,000 to 1/5,500 (weight ratio), more preferablyfrom 1/1,000 to 1/2,000 (weight ratio), furthermore preferably from1/1,300 to 1/1,900. As the ratio of the total organic lithium compoundinitiator amount to the charge amount of the third stage organic lithiumcompound initiator, the total organic lithium compound initiator/thirdstage organic lithium compound initiator is preferably from 1.05/1 to6/1 (molar ratio), more preferably from 1.3/1 to 2.1/1 (molar ratio).Further, as the ratio of the total monomer amount to the charge amountof the third stage vinyl aromatic hydrocarbon, the total monomeramount/third stage vinyl aromatic hydrocarbon is preferably from 6/1 to10/1 (weight ratio), more preferably from 7/1 to 9/1 (weight ratio).

After the vinyl aromatic hydrocarbon is added and polymerization iscontinued at a predetermined temperature, complete completion of thepolymerization reaction is taken as the end point of the third stagepolymerization. It is preferred that after completion of the third stagepolymerization, a predetermined amount of a conjugated diene is newlyadded to the polymerization system to initiate a fourth stagepolymerization. The end point of the polymerization can be judged bymeasuring the solid content concentration of a sampled polymer liquid toconfirm whether or not a polymer at a predetermined concentration isformed. Otherwise, it may be judged by confirming that substantially nounreacted monomer remains by e.g. gas chromatography.

In the fourth stage polymerization, the charge amount is determined toobtain an aimed molecular weight and then a conjugated diene is added.As the ratio of the charge amount of the conjugated diene to the totalmonomer amount, the conjugated diene/total monomer amount is preferablyfrom 2.5/1 to 5/1 (weight ratio), more preferably from 2.9/1 to 4/1(weight ratio). After the conjugated diene is added and polymerizationis continued at a predetermined temperature, the complete completion ofthe polymerization reaction is taken as the end point of the fourthstage polymerization. The end point of the polymerization can be judgedby measuring the solid content concentration of a sampled polymer liquidto confirm whether or not a polymer at a predetermined concentration isformed.

In a fifth stage polymerization, the charge amount is determined toobtain an aimed molecular weight and then a vinyl aromatic hydrocarbonis added. As the ratio of the total monomer amount to the charge amountof the fifth stage vinyl aromatic hydrocarbon, the total monomeramount/fifth stage vinyl aromatic hydrocarbon is preferably from 6/1 to10/1 (weight ratio), more preferably from 7/1 to 9/1 (weight ratio).After the vinyl aromatic hydrocarbon is added and polymerization iscontinued at a predetermined temperature, complete completion of thepolymerization reaction is taken as the end point of the fifth stagepolymerization. Then, all active terminals in an active polymer chainmay be inactivated by a polymerization terminator such as water or analcohol in an amount sufficient to inactivate all active terminals, oronly part of active terminals may be inactivated by addition of apolymerization terminator such as water or an alcohol and as the caserequires, a solvent, in an amount to inactivate only part of activeterminals so that living anionic polymerization is continued, and then asixth stage polymerization is carried out. As the number of remainingactive terminals at the sixth stage polymerization, the number of activeterminals at the fifth stage polymerization/number of active terminalsat the sixth stage polymerization is preferably from 1.05 to 2.5, morepreferably from 1.1 to 2. The end point of the polymerization can bejudged by measuring the solid content concentration of a sampled polymerliquid to confirm whether or not a polymer at a predeterminedconcentration is formed. Otherwise, it may be judged by confirming thatsubstantially no unreacted monomer remains by e.g. gas chromatography.

When only part of active terminals are inactivated and the livinganionic polymerization is continued, the sixth stage polymerization iscarried out. In the sixth stage polymerization, the charge amount isdetermined to obtain an aimed molecular weight and then a vinyl aromatichydrocarbon is added. As the ratio of the total monomer amount to thecharge amount of the sixth stage vinyl aromatic hydrocarbon, the totalmonomer amount/sixth stage vinyl aromatic hydrocarbon is preferably from10/1 to 30/1 (weight ratio), more preferably from 14/1 to 25/1 (weightratio). After a vinyl aromatic hydrocarbon is added and polymerizationis continued at a predetermined temperature, complete completion of thepolymerization reaction is taken as the end point of the sixth stagepolymerization. The end point of the polymerization can be judged bymeasuring the solid content concentration of a sampled polymer liquid toconfirm whether or not a polymer at a predetermined concentration isformed. Otherwise, it may be judged by confirming that substantially nounreacted monomer remains by e.g. gas chromatography. After completionof the sixth stage polymerization, it is preferred to inactivate allactive terminals of an active polymer chain by a polymerizationterminator such as water or an alcohol in an amount sufficient toinactivate all active terminals.

As mentioned above, by properly controlling the amounts of the initiatorin the first, second and third stage polymerization, the amounts of thevinyl aromatic hydrocarbon in the first, second, third, fifth and sixthstage polymerization, and the ratio of active terminals inactivated atthe end point of the fifth stage polymerization, a linear blockcopolymer composition can be obtained, characterized in that it has atleast three types of polymer blocks with different molecular weightseach comprising a vinyl aromatic hydrocarbon as monomer units, (1) themolecular weight distribution (Mw/Mn) of a mixture of the polymer blockseach comprising a vinyl aromatic hydrocarbon as monomer units is withina range of from 3.35 to 6, and (2) in a gel permeation chromatogram of amixture of the polymer blocks each comprising a vinyl aromatichydrocarbon as monomer units, M1/M2 is within a range of from 12.5 to25, where M1 is the peak top molecular weight corresponding to a peak atwhich the peak top molecular weight becomes maximum among peaks forminga proportion of the area of at least 30% to the whole peak area, and M2is the peak top molecular weight corresponding to a peak at which thepeak top molecular weight becomes minimum among peaks at which the peaktop molecular weight is at most 50,000 and which forms a proportion ofthe area of at least 20% to the whole peak area.

With the linear block copolymer composition of the present invention,various additives may further be blended as the case requires.

In a case where the block copolymer composition is subjected to a heattreatment, or to prevent deterioration of physical properties when amolded product of the composition is used in an oxidizing atmosphere orunder irradiation with e.g. ultraviolet rays, or to further improvephysical properties suitable for the purpose of use, an additive such asa stabilizer, a lubricant, a processing aid, an antiblocking agent, anantistatic agent, an antifogging agent, a weather resistance-improvingagent, a softening agent, a plasticizer or a pigment may, for example,be added.

The stabilizer may, for example, be2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenylacrylate,2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, or a phenol antioxidant such asoctadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate or2,6-di-tert-butyl-4-methylphenol, or a phosphorus antioxidant such as2,2-methylenebis (4,6-di-tert-butylphenyl)octyl phosphite,trisnonylphenyl phosphite or bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-di-phosphite.

Further, the lubricant, processing acid, antiblocking agent, antistaticagent or antifogging agent may, for example, be a saturated fatty acidsuch as palmitic acid, stearic acid or behenic acid, a fatty acid esteror a pentaerythritol fatty acid ester such as octyl palmitate or octylstearate, a fatty acid amide such as erucamide, oleamide or stearamide,or an ethylenebisstearamide, a glycerol-mono-fatty acid ester, aglycerol-di-fatty acid ester, a sorbitan fatty acid ester such assorbitan-mono-palmitate or sorbitan-mono-stearate, or a higher alcoholsuch as myristyl alcohol, cetyl alcohol or stearyl alcohol.

Further, the weather resistance-improving agent may, for example, be abenzotriazole type such as2-(2′-hydroxy-3′-tert-butyl-5′-methylphenyl)-5-chlorobenzotriazole, asalicylate type such as2,4-di-tert-butylphenyl-3′,5′-di-tert-butyl-4′-hydroxybenzoate, abenzophenone type ultraviolet absorber such as2-hydroxy-4-n-octoxybenzophenone, or a hindered amine type weatherresistance-improving agent such astetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate.Further, white oil or silicone oil may, for example, be added.

Such an additive is used in an amount of preferably at most 5 mass %,particularly preferably from 0 to 3 mass %, in the linear blockcopolymer composition of the present invention.

The linear block copolymer composition thus obtained can be easilymolded and processed into various practically useful products such assheets, foams, films, and injection molded products, blow moldedproducts, pressure molded products, vacuum molded products and biaxiallyoriented products having various shapes, etc., by an optionalconventional molding or processing method such as extrusion, injectionmolding or blow molding.

The linear block copolymer composition of the present invention may beblended with a thermoplastic resin as the case requires to form a resincomposition.

As examples of the thermoplastic resin to be used, a polystyrenepolymer, a polyphenylene ether polymer, a polyethylene polymer, apolypropylene polymer, a polybutene polymer, a polyvinyl chloridepolymer, a polyvinyl acetate polymer, a polyamide polymer, athermoplastic polyester polymer, a polyacrylate polymer, a polyphenoxypolymer, a polyphenylene sulfide polymer, a polycarbonate polymer, apolyacetal polymer, a polybutadiene polymer, a thermoplasticpolyurethane polymer and a polysulfin polymer may, for example, bementioned. A preferred thermoplastic resin is a styrene polymer, and apolystyrene resin, a styrene-butyl acrylate copolymer or astyrene-methyl methacrylate copolymer is particularly preferably used.

As the blend mass ratio of the linear block copolymer composition of thepresent invention to the thermoplastic resin, the linear block copolymercomposition/thermoplastic resin is preferably from 3/97 to 90/10. If theblend amount of the block copolymer is less than 3 mass %, no sufficienteffect of improving impact resistance of the formed resin compositionwill be obtained, and if the blend amount of the thermoplastic resin isless than 10 mass %, no sufficient effect of improving rigidity, etc. byblending the thermoplastic resin will be obtained. As a particularlypreferred blend mass ratio of the linear block copolymer composition tothe thermoplastic resin, the linear block copolymercomposition/thermoplastic resin is from 30/70 to 80/20, more preferablyfrom 40/60 to 70/30.

Now, the present invention will be explained in further detail withreference to Examples of the present invention. However, the presentinvention is by no means restricted to such specific Examples.

Data shown in Examples and Comparative Examples were measured inaccordance with the following methods.

The peak top molecular weight as calculated as polystyrene and themolecular weight distribution of a linear block copolymer composition,and the molecular weight distribution of a component corresponding to apeak at which the peak top molecular weight becomes maximum among peaksforming a proportion of the area of at least 30% to the whole peak areaof the linear block copolymer composition, were determined by means of aGPC method under the measurement conditions 2.

The proportion of the area of each peak to the whole peak area in achromatogram of the linear block copolymer composition was determined insuch a manner that the area of a portion surrounded by the base line andperpendiculars drawn from valleys between peaks to the base line wascalculated with respect to each peak and the proportion of the area ofeach peak to the whole area of the chromatogram of the linear blockcopolymer composition was obtained as a percentage.

The molecular weight distribution of a component corresponding to a peakat which the peak top molecular weight becomes maximum among peaksforming a proportion of the area of at least 30% to the whole peak areaof the linear block copolymer composition, was determined in such amanner that such a peak was selected in a chromatogram of the linearblock copolymer composition, perpendiculars were drawn from valleysbetween adjacent peaks to the base line, and the peak at a portionsurrounded by the base line and the perpendiculars was employed tocalculate the molecular weight distribution.

Further, the peak top molecular weight as calculated as polystyrene andthe molecular weight distribution of polymer blocks comprising a vinylaromatic hydrocarbon as monomer units were determined by measuring apolymer content obtained by subjecting the linear block copolymercomposition to ozonolysis and then reduction with lithium aluminumhydride by means of a GPC method under the measurement conditions 1. Theproportion of the area of each peak to the whole peak area in achromatogram of the polymer block comprising a vinyl aromatichydrocarbon as monomer units was determined similarly to thedetermination of the proportion of the area of each peak to the wholepeak area in a chromatogram of the linear block copolymer composition,in such a manner that the area of a portion surrounded by the base lineand perpendiculars drawn from valleys between peaks to the base line wascalculated with respect to each peak, and the proportion of the area ofeach peak to the whole area of the chromatogram of the linear blockcopolymer composition was obtained as a percentage.

The total luminous transmittance and the haze were measured inaccordance with JIS-K7105 and the Charpy impact strength was measured inaccordance with JIS K-7111 (notched) by molding a test specimen fromresin pellets by a injection molding machine. Similarly, the fallingweight impact strength was measured in such a manner that a flat platewith a thickness of 2 mm was formed by an injection molding machine, andby using a Falling Weight type Graphic Impact Tester (trade mark forinstrumented falling weight impact tester manufactured by Toyo SeikiSeisaku-Sho, Ltd.), a heavy weight with a mass of 6.5 kg was made tofreely fall from a height of 62 cm on the plane of the test specimenfixed in a holder (diameter: 40 mm), and the test specimen wascompletely destroyed or pierced by means of a striker (diameter: 12.7mm) provided at the bottom of the heavy weight, and the total energy(hereinafter referred to as total absorbed energy) required at this timewas measured. Further, the amount of a polybutadiene rubber component(PBd amount) in the linear block copolymer composition was determined bya halogen addition method of adding iodine chloride to a double bond.Further, fluidity (MFR) at a high temperature was measured in accordancewith JIS K-7210.

EXAMPLE 1

A linear block copolymer composition is obtained by a conventionalliving anionic polymerization method using an organic lithium compoundas an initiator in a hydrocarbon solvent.

Specifically, a jacketed stainless steel polymerization tank equippedwith a stirrer, having an internal volume of 10 L, was washed withcyclohexane, and the air in the polymerization tank was replaced withnitrogen, and then 4,200 g of cyclohexane dehydrated to a moisturecontent of at most 7 ppm, containing 150 ppm of tetrahydrofuran, wascharged into the polymerization tank, and then 377 g of styrenedehydrated to a moisture content of at most 7 ppm was added. Theinternal temperature was increased to 50° C., and then 4.2 ml of an-butyllithium 10 mass % cyclohexane solution was added, andpolymerization was carried out for 20 minutes so that the maximumtemperature would not exceed 120° C. (first stage polymerization).

Then, at a constant internal temperature of 50° C., 4.7 ml of an-butyllithium 10 mass % cyclohexane solution and then 80 g of styrenedehydrated to a moisture content of at most 7 ppm were added, andpolymerization was carried out for 20 minutes so that the maximumtemperature would no exceed 120° C. (second stage polymerization).

Then, at a constant internal temperature of 50° C., 7.8 ml of an-butyllithium 10 mass % cyclohexane solution and then 142 g of styrenedehydrated to a moisture content of at most 7 ppm were added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (third stage polymerization).

Further, the internal temperature was increased to 80° C., and then 310g of butadiene dehydrated by being passed through molecular sieves wasadded, and polymerization was carried out for 20 minutes so that themaximum temperature would not exceed 120° C. (fourth stagepolymerization).

Then, at a constant internal temperature of 80° C., 142 g of styrenedehydrated to a moisture content of at most 7 ppm was added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (fifth stage polymerization).

Finally, all polymer active terminals were inactivated by methanol.2,4-Bis[(octylthio)methyl]-o-cresol as a stabilizer was added in aproportion of 0.2 mass % per 100 parts by mass of the polymer, and thenthe polymer liquid was diluted with cyclohexane, and the obtainedsolution was poured into a large amount of methanol to precipitate apolymer content, which was vacuum-dried to obtain a powdery polymer.

The obtained powdery polymer was supplied to a 20 mm single screwextruder, and a molten strand was withdrawn from a die at 210° C.,cooled with water and cut by a cutter to obtain resin pellets.

The charge amounts are shown in Table 1, analyzed values are shown inTables 2 and 3, and results of evaluation of solid physical propertiesare shown in Table 4.

Further, a chromatogram of the linear block copolymer composition ofExample 1 measured under the measurement conditions 2 is shown in FIG.1, and a chromatogram of a polymer content obtained by subjecting theobtained linear block copolymer composition to ozonolysis and thenreduction with lithium aluminum hydride is shown in FIG. 2.

EXAMPLES 2 AND 3 AND COMPARATIVE EXAMPLES 1 TO 4

Pellets were obtained in formulae as shown in Table 1 in the same manneras in Example 1.

Analyzed values are shown in Tables 2 and 3 and results of evaluation ofsolid physical properties are shown in Table 4. TABLE 1 Amount ofmaterials charged Comp. Comp. Comp. Comp. Example 1 Example 2 Example 3Ex. 1 Ex. 2 Ex. 3 Ex. 4 Solvent cyclohexane (g) 4200 4360 4370 4400 43704410 4380 Solvent/total monomer amount 4.0 4.0 4.0 4.0 4.0 4.0 4.0(weight ratio) First stage n-BuLi 10% 4.2 4.5 4.8 3.9 5.2 6.6 4.8cyclohexane solution (ml) First stage styrene (g) 377 406 387 334 493397 371 Second stage n-BuLi 10% 4.7 1.6 5.3 1.4 4.1 5.5 3.7 cyclohexanesolution (ml) Second stage styrene (g) 80 52 83 43 84 113 228 Thirdstage n-BuLi 10% 7.8 10.4 8.8 9.6 2 2.8 1.9 cyclohexane solution (ml)Third stage styrene (g) 142 147 145 126 93 126 84 Fourth stage butadiene(g) 310 340 334 330 327 327 329 Fifth stage styrene (g) 142 147 145 26893 126 84

TABLE 2 Analyzed values of polymer content obtained after ozonolysis oflinear block copolymer composition Comp. Comp. Comp. Example 1 Example 2Example 3 Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 GPC measurement conditions 1 1 11 1 1 1 Peak top molecular weight M1 126000 136000 132000 107000 12600082000 128000 Peak top molecular weight M2 8800 8800 8300 17500 8500 84008600 Peak top molecular weight M5 22000 24000 19000 No peak 19900 2100011800 satisfying conditions detected Proportion (%) of number of 10.79.0 7.5 15.4 27.5 28.0 25.0 moles of component S1 to the sum of numbersof moles of components S1 and S2 M1/M2 14.3 15.5 15.9 6.11 14.8 9.7614.9 M5/M2 2.50 2.73 2.29 2.34 2.50 1.37 Molecular weight distribution3.61 4.21 3.89 2.83 2.90 2.45 2.69 (Mw/Mn)

TABLE 3 Analyzed values of linear block copolymer composition Comp.Comp. Comp. Comp. Example 1 Example 2 Example 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4GPC measurement conditions 2 2 2 2 2 2 2 Molecular weight 1.004 1.0041.004 1.006 1.004 1.004 1.005 distribution of a component at which thepeak top molecular weight becomes maximum among peaks forming aproportion of at least 30% (Mw/Mn) Peak top molecular weight 174200191000 185300 181000 164000 123000 165000 M3 Peak top molecular weight50300 53100 51400 75000 57000 55000 55000 M4 M3/M4 3.5 3.6 3.6 2.4 2.92.2 3.0 Peak top molecular weight 174200 191000 185300 181000 164000123000 165000 of a component providing a maximum peak

TABLE 4 Results of measurement of physical properties of linear blockcopolymer composition Comp. Comp. Comp. Comp. Example 1 Example 2Example 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 PBd amount (%) 29 31 31 29 30 30 30MFR (g/10 min) 12.3 10.1 9.9 7.6 11 31.1 9.7 Haze (%) 1.3 1.5 1.5 1.41.4 1.4 1.5 Total luminous transmittance (%) 90 88.7 89 90 89.8 90.188.9 Total absorbed energy (J) 15.5 16.3 16.5 7 9.9 3.5 4.9 Charpyimpact strength (kJ/m) 2.9 9.8 7.8 1.1 1.2 1.1 1.1

EXAMPLE 4

A jacketed stainless steel polymerization tank equipped with a stirrer,having an internal volume of 10 L, was washed with cyclohexane, and theair in the polymerization tank was replaced with nitrogen, and then4,400 g of cyclohexane dehydrated to a moisture content of at most 7ppm, containing 150 ppm of tetrahydrofuran, was charged into thepolymerization tank, and then 360 g of styrene dehydrated to a moisturecontent of at most 7 ppm was added. The internal temperature wasincreased to 50° C., and then 3.0 ml of a n-butyllithium 10 mass %cyclohexane solution was added, and polymerization was carried out for20 minutes so that the maximum temperature would not exceed 120° C.(first stage polymerization).

Then, at a constant internal temperature of 50° C., 1.5 ml of an-butyllithium 10 mass % cyclohexane solution and then 45 g of styrenedehydrated to a moisture content of at most 7 ppm were added, andpolymerization was carried out for 20 minutes so that the maximumtemperature would no exceed 120° C. (second stage polymerization).

Then, at a constant internal temperature of 50° C., 10.4 ml of an-butyllithium 10 mass % cyclohexane solution and then 136 g of styrenedehydrated to a moisture content of at most 7 ppm were added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (third stage polymerization).

Further, the internal temperature was increased to 80° C., and then 340g of butadiene dehydrated by being passed through molecular sieves wasadded, and polymerization was carried out for 20 minutes so that themaximum temperature would not exceed 120° C. (fourth stagepolymerization).

Then, at a constant internal temperature of 80° C., 136 g of styrenedehydrated to a moisture content of at most 7 ppm was added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (fifth stage polymerization).

Further, 0.28 g of water dispersed in 30 ml of cyclohexane was added toinactivate part of polymer active terminals, and then 73 g of styrenedehydrated to a moisture content of at most 7 ppm was added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (sixth stage polymerization).

Finally, all polymer active terminals were inactivated by methanol.2,4-Bis[(octylthio)methyl]-o-cresol as a stabilizer was added in aproportion of 0.2 mass % per 100 parts by mass of the polymer, and thenthe polymer liquid was diluted with cyclohexane, and the obtainedsolution was poured into a large amount of methanol to precipitate apolymer content, which was vacuum-dried to obtain a powdery polymer.

The obtained powdery polymer was supplied to a 20 mm single screwextruder, and a molten strand was withdrawn from a die at 210° C.,cooled with water and cut by a cutter to obtain resin pellets. Thecharge amounts are shown in Table 5, analyzed values are shown in Tables6 and 7, and results of evaluation of solid physical properties areshown in Table 8.

EXAMPLE 5 AND COMPARATIVE EXAMPLES 5 AND 6

Powdery polymers were obtained in formulae as shown in Table 5 in thesame manner as in Example 4.

Analyzed values are shown in Tables 6 to 7, and results of evaluation ofsolid physical properties are shown in Table 8. TABLE 5 Amount ofmaterials charged Comp. Comp. Example 4 Example 5 Ex. 5 Ex. 6 Solventcyclohexane (g) 4360 4360 4390 4410 Solvent/total monomer 4.0 4.0 4.04.0 amount (weight ratio) First stage n-BuLi 10% 3 3 4 4.5 cyclohexanesolution (ml) First stage styrene (g) 360 360 346 322 Second stagen-BuLi 10% 1.5 1.5 5.7 6.8 cyclohexane solution (ml) Second stagestyrene (g) 46 46 88 140 Third stage n-BuLi 10% 10.4 10.4 5.7 6.8cyclohexane solution (ml) Third stage styrene (g) 136 136 131 97 Fourthstage butadiene 340 340 329 331 (g) Fifth stage styrene (g) 136 136 13197 Sixth stage water (g) 0.28 0.16 0.15 0.18 Sixth stage styrene (g) 7373 73 116

TABLE 6 Analyzed values of polymer content obtained after ozonolysis oflinear block copolymer composition Comp. Example 4 Example 5 Ex. 5 Comp.Ex. 6 GPC measurement 1 1 1 1 conditions Peak top molecular 113000122000 117000 99000 weight M1 Peak top molecular 8500 9100 5800 18000weight M2 Peak top molecular 22000 21000 29000 No peak weight M5satisfying conditions detected Proportion (%) of 11.0 14.2 18.2 16.7number of moles of component S1 to the sum of numbers of moles ofcomponents S1 and S2 M1/M2 13.3 13.4 20.2 5.50 M5/M2 2.59 2.31 5.00Molecular weight 3.70 3.42 3.01 2.92 distribution (Mw/Mn)

TABLE 7 Analyzed values of linear block copolymer composition Comp.Comp. Example 4 Example 5 Ex. 5 Ex. 6 GPC measurement 2 2 2 2 conditionsMolecular weight 1.004 1.004 1.004 1.003 distribution of a component atwhich the peak top molecular weight becomes maximum among peaks forminga proportion of the area of at least 30% to the whole peak area (Mw/Mn)Peak top molecular 165140 169000 169000 144000 weight M3 Peak topmolecular 54000 54000 50600 48000 weight M4 M3/M4 3.1 3.1 3.3 3.0 Peaktop molecular 165140 169000 169000 144000 weight of a componentproviding a maximum peak

TABLE 8 Results of measurement of physical properties of linear blockcopolymer composition Comp. Comp. Example 4 Example 5 Ex. 5 Ex. 6 PBdamount (%) 31 31 30 30 MFR (g/10 min) 11.1 9.7 7.7 25.1 Haze (%) 1.4 1.61.3 1.6 Total luminous 90 87 90 87.1 transmittance (%) Total absorbedenergy (J) 16.5 18.1 6.1 9.9 Charpy impact strength 5.6 9.9 1.2 1.1(kJ/m)

REFERENCE EXAMPLE 1

Polymerization was carried out in a formula as shown in Table 9 in thesame manner as in Example 1. TABLE 9 Amount of materials chargedReference Example 1 Solvent cyclohexane (g) 4200 Solvent/total monomer4.1 amount (weight ratio) First stage n-BuLi 10% 4 cyclohexane solution(ml) First stage styrene (g) 360 Second stage n-BuLi 10% 1.5 cyclohexanesolution (ml) Second stage styrene (g) 46 Third stage n-BuLi 10% 10.1cyclohexane solution (ml) Third stage styrene (g) 136 Fourth stagebutadiene (g) 338 Fifth stage styrene (g) 136

EXAMPLE 6

260 g of the powdery polymer obtained in the above Reference Example 1and 250 g of the powdery polymer obtained in Comparative Example 2 wereblended and supplied to a 20 mm single screw extruder, and a moltenstrand was withdrawn from a die at 210° C., cooled with water and cut bya cutter to obtain resin pellets.

Analyzed values are shown in Tables 10 and 11, and results of evaluationof solid physical properties are shown in Table 12. TABLE 10 Analyzedvalues of polymer content obtained after ozonolysis of linear blockcopolymer composition Example 6 Example 7 Comp. Ex. 7 Comp. Ex. 8 GPCmeasurement conditions 1 1 1 1 Peak top molecular weight M1 114000115000 114000 115000 Peak top molecular weight 8800 9000 8800 9000 M2Peak top molecular weight 21000 20000 21000 21000 M5 Proportion (%) ofnumber of moles 14.3 11.8 18.2 26.7 of component S1 to the sum ofnumbers of moles of components S1 and S2 M1/M2 13.0 12.8 13.0 12.8 M5/M22.39 2.22 2.39 2.33 Molecular weight 3.45 3.42 2.89 2.65 distribution(Mw/Mn)

TABLE 11 Analyzed values of linear block copolymer composition Comp.Comp. Example 6 Example 7 Ex. 7 Ex. 8 GPC measurement 2 2 2 2 conditionsMolecular weight 1.017 1.025 1.023 1.025 distribution of a component atwhich the peak top molecular weight becomes maximum among peaks forminga proportion of the area of at least 30% to the whole peak area (Mw/Mn)Peak top molecular 175000 177500 175000 177500 weight M3 Peak topmolecular 56000 57500 56000 57500 weight M4 M3/M4 3.1 3.1 3.1 3.1 Peaktop molecular 175000 177500 175000 177500 weight of a componentproviding a maximum peak

TABLE 12 Results of measurement of physical properties of linear blockcopolymer composition Comp. Comp. Example 6 Example 7 Ex. 7 Ex. 8 PBdamount (%) 30 30 29 28 MFR (g/10 min) 12.1 10.5 11.8 11.5 Haze (%) 1.31.3 1.2 1.2 Total luminous 89.1 89 90.1 89.8 transmittance (%) Totalabsorbed energy (J) 16.5 15.5 4.5 5.6 Charpy impact strength 5.9 6.1 1.11.2 (kJ/m)

COMPARATIVE EXAMPLE 7

260 g of the powdery polymer obtained in Reference Example 1 and 350 gof the powdery polymer obtained in Comparative Example 2 were blendedand supplied to a 20 mm single screw extruder, and a molten strand waswithdrawn from a die at 210° C., cooled with water and cut by a cutterto obtain resin pellets.

Analyzed values are shown in Tables 10 and 11, and results of evaluationof solid physical properties are shown in Table 12.

REFERENCE EXAMPLE 2

A powdery polymer was obtained in a formula as shown in Table 13 inaccordance with the following procedure.

A jacketed stainless steel polymerization tank equipped with a stirrer,having an internal volume of 3 L, was washed with cyclohexane, and theair in the polymerization tank was replaced with nitrogen, and then1,360 g of cyclohexane dehydrated to a moisture content of at most 7ppm, containing 150 ppm of tetrahydrofuran, was charged into thepolymerization tank, and then 257 g of styrene dehydrated to a moisturecontent of at most 7 ppm was added. The internal temperature wasincreased to 50° C., and then 2.0 ml of a n-butyllithium 10 mass %cyclohexane solution was added, and polymerization was carried out for20 minutes so that the maximum temperature would not exceed 120° C.(first stage polymerization).

Then, the internal temperature was increased to 80° C., and 33 g ofbutadiene dehydrated by being passed through molecular sieves was added,and polymerization was carried out for 20 minutes so that the maximumtemperature would not exceed 120° C. (second stage polymerization).

Then, at a constant internal temperature of 80° C., 37 g of styrenedehydrated to a moisture content of at most 7 ppm was added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (third stage polymerization).

Finally, all polymer active terminals were inactivated by methanol.2,4-Bis[(octylthio)methyl]-O-cresol as a stabilizer was added in aproportion of 0.2 mass % per 100 parts by mass of the polymer, and thenthe polymer liquid was diluted with cyclohexane, and the obtainedsolution was poured into a large amount of methanol to precipitate apolymer content, which was vacuum-dried to obtain a powdery polymer.TABLE 13 Amount of materials charged Reference Example 2 Solventcyclohexane (g) 1360 Solvent/total monomer 4.2 amount (weight ratio)First stage n-BuLi 10% 2.1 cyclohexane solution (ml) First stage styrene(g) 257 Second stage butadiene (g) 33 Third stage styrene (g) 37

EXAMPLE 7

325 g of the powdery polymer obtained in Reference Example 1 and 50 g ofthe powdery polymer obtained in Reference Example 2 as describedhereinafter were blended and supplied to a 20 mm single screw extruder,and a molten strand was withdrawn from a die at 210° C., cooled withwater and cut by a cutter to obtain resin pellets.

Analyzed values are shown in Tables 10 and 11, and results of evaluationof solid physical properties are shown in Table 12.

COMPARATIVE EXAMPLE 8

250 g of the powdery polymer obtained in Reference Example 1 and 100 gof the powdery polymer obtained in Reference Example 2 were blended andsupplied to a 20 mm single screw extruder, and a molten strand waswithdrawn from a die at 210° C., cooled with water and cut by a cutterto obtain resin pellets.

Analyzed values are shown in Tables 10 and 11, and results of evaluationof solid physical properties are shown in Table 12.

COMPARATIVE EXAMPLE 9

A jacketed stainless steel polymerization tank equipped with a stirrer,having an internal volume of 10 L, was washed with cyclohexane, and theair in the polymerization tank was replaced with nitrogen, and then4,360 g of cyclohexane dehydrated to a moisture content of at most 7ppm, containing 150 ppm of tetrahydrofuran, was charged into thepolymerization tank, and then 474 g of styrene dehydrated to a moisturecontent of at most 7 ppm was added. The internal temperature wasincreased to 50° C., and then 5.2 ml of a n-butyllithium 10 mass %cyclohexane solution was added, and polymerization was carried out for20 minutes so that the maximum temperature would not exceed 120° C.(first stage polymerization).

Then, at a constant internal temperature of 50° C., 6.9 ml of an-butyllithium 10 mass % cyclohexane solution and then 209 g of styrenedehydrated to a moisture content of at most 7 ppm were added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would no exceed 120° C. (second stage polymerization).

Further, the internal temperature was increased to 80° C., and then 310g of butadiene dehydrated by being passed through molecular sieves wasadded, and polymerization was carried out for 20 minutes so that themaximum temperature would not exceed 120° C. (third stagepolymerization).

Then, at a constant internal temperature of 80° C., 100 g of styrenedehydrated to a moisture content of at most 7 ppm was added, andpolymerization was carried out for 15 minutes so that the maximumtemperature would not exceed 120° C. (fourth stage polymerization).

Finally, all polymer active terminals were inactivated by methanol.2,4-Bis[(octylthio)methyl]-o-cresol as a stabilizer was added in aproportion of 0.2 mass % per 100 parts by mass of the polymer, and thenthe polymer liquid was diluted with cyclohexane, and the obtainedsolution was poured into a large amount of methanol to precipitate apolymer content, which was vacuum-dried to obtain a powdery polymer.

The obtained powdery polymer was supplied to a 20 mm single screwextruder, and a molten strand was withdrawn from a die at 210° C.,cooled with water and cut by a cutter to obtain resin pellets.

The charge amounts are shown in Table 14, analyzed values are shown inTables 15 and 16, and results of evaluation of solid physical propertiesare shown in Table 17.

COMPARATIVE EXAMPLES 10 AND 11

Pellets were obtained in formulae as shown in Table 14 in the samemanner as in Comparative Example 9.

Analyzed values are shown in Tables 15 and 16, and results of evaluationof solid physical properties are shown in Table 17. TABLE 14 Amount ofmaterials charged Comp. Ex. Comp. Ex. Comp. Ex. 9 10 11 Solventcyclohexane (g) 4360 4389 4453 Solvent/total monomer 4.0 4.2 4.5 amount(weight ratio) First stage n-BuLi 10% 5.2 4 5 cyclohexane solution (ml)First stage styrene (g) 474 348 484 Second stage n-BuLi 10% 6.9 11 5.7cyclohexane solution (ml) Second stage styrene (g) 209 188 93 Thirdstage butadiene (g) 310 329 315 Fourth stage styrene (g) 100 188 93

TABLE 15 Analyzed values of polymer content obtained after ozonolysis oflinear block copolymer composition Comp. Ex. 9 Comp. Ex. 10 Comp. Ex. 11GPC measurement 1 1 1 conditions Peak top molecular 138000 123000 123000weight M1 Peak top molecular 21000 12000 8100 weight M2 Peak topmolecular No peak No peak No peak weight M5 satisfying satisfyingsatisfying conditions conditions conditions detected detected detectedProportion (%) of 26.4 10.0 19.6 number of moles of component S1 to thesum of numbers of moles of components S1 and S2 M1/M2 6.57 10.3 15.2M5/M2 Molecular weight 2.82 3.09 3.45 distribution (Mw/Mn)

TABLE 16 Analyzed values of linear block copolymer composition Comp.Comp. Comp. Ex. 9 Ex. 10 Ex. 11 GPC measurement conditions 2 2 2Molecular weight 1.005 1.004 1.003 distribution of a component at whichthe peak top molecular weight becomes maximum among peaks forming aproportion of the area of at least 30% to the whole peak area (Mw/Mn)Peak top molecular weight 203200 155000 148000 M3 Peak top molecularweight 81000 38000 36000 M4 M3/M4 2.5 4.1 4.1 Peak top molecular weightof 203200 155000 148000 a component providing a maximum peak

TABLE 17 Results of measurement of physical properties of linear blockcopolymer composition Comp. Comp. Comp. Ex. 9 Ex. 10 Ex. 11 PBd amount(%) 28 31 32 MFR (g/10 min) 6.9 15.9 20.5 Haze (%) 1.1 1.2 1.2 Totalluminous transmittance 90.5 90 90 (%) Total absorbed energy (J) 7.4 98.9 Charpy impact strength (kJ/m) 1.2 1.2 1.2

EXAMPLES 8 TO 14 AND COMPARATIVE EXAMPLE 12 TO 22

Each of the linear block copolymer compositions obtained in Examples 1to 7 and Comparative Examples l to ll and a general purpose polystyrene(Gl4L, manufactured by TOYO STYRENE CO., LTD.) were blended in a weightratio of linear block copolymer composition/general purpose polystyreneof 6/4 and supplied to a 20 mm single screw extruder, and then a meltstrand was withdrawn from a die at 230° C., cooled with water and cut bya cutter to obtain resin pellets. Then, physical properties wereevaluated in the same manner as in Example 1. The results are shown inTables 18 to 20. TABLE 18 Results of measurement of physical propertiesof blended product of linear block copolymer composition and generalpurpose polystyrene Example 8 Example 9 Example 10 Example 11 Example 12Example 13 Example 14 Linear block Copolymer Copolymer CopolymerCopolymer Copolymer Copolymer Copolymer copolymer compositioncomposition composition composition composition composition compositioncomposition of Ex. 1 of Ex. 2 of Ex. 3 of Ex. 4 of Ex. 5 of Ex. 6 of Ex.7 used MFR (g/10 min) 11.3 10.8 9.7 8.1 7.5 8.8 14.9 Haze (%) 2 8.5 76.5 6.9 5.5 3.5 Total 84.8 79.9 80.5 82.4 81.5 82.9 84 luminoustransmittance (%) Total 3.1 15.6 14.5 12.7 16.8 11.9 6.5 absorbed energy(J) Charpy impact 1.2 1.3 1.4 1.3 1.5 1.3 1.3 strength (kJ/m)

TABLE 19 Results of measurement of physical properties of blendedproduct of linear block copolymer composition and general purposepolystyrene Comp. Ex. 12 Comp. Ex. 13 Comp. Ex. 14 Comp. Ex. 15 Comp.Ex. 16 Comp. Ex. 17 Linear block Copolymer Copolymer Copolymer CopolymerCopolymer Copolymer copolymer composition composition compositioncomposition composition composition composition of Comp. Ex. 1 of Comp.Ex. 2 of Comp. Ex. 3 of Comp. Ex. 4 of Comp. Ex. 5 of Comp. Ex. 6 usedMFR (g/10 min) 6.3 9 15.8 6.9 5.3 15 Haze (%) 4 3.3 3.9 3.5 2.8 2.5Total 81.1 84.5 82.1 83.5 85.5 86 luminous transmittance (%) Total 1.50.8 0.9 1.9 0.9 1.3 absorbed energy (J) Charpy impact 1.8 1.1 0.9 0.91.1 1.2 strength (kJ/m)

TABLE 20 Results of measurement of physical properties of blendedproduct of linear block copolymer composition and general purposepolystyrene Comp. Ex. 18 Comp. Ex. 19 Comp. Ex. 20 Comp. Ex. 21 Comp.Ex. 22 Linear block Copolymer Copolymer Copolymer Copolymer Copolymercopolymer composition composition composition composition compositioncomposition of Comp. Ex. 7 of Comp. Ex. 8 of Comp. Ex. 9 of Comp. Ex. ofComp. Ex. used 10 11 MFR (g/10 min) 8.8 5.9 2.8 10.3 14.9 Haze (%) 4 3.93.8 4.2 3.5 Total 81.1 81.5 84.8 83.1 84 luminous transmittance (%)Total 1.2 0.8 1.1 1.9 1.5 absorbed energy (J) Charpy impact 1.3 1.4 1.81 1 strength (kJ/m)

INDUSTRIAL APPLICABILITY

The linear block copolymer composition of the present invention isuseful for applications to which a conventional block copolymer is used,such as modifiers for various thermoplastic resins and thermosettingresins, raw materials for footwear, raw materials for tackifiers andadhesives, modifiers for asphalt, raw materials for wire cables andmodifiers for vulcanized rubber. Particularly, a composition obtained byblending the linear block copolymer composition of the present inventionwith a thermoplastic resin is useful as a raw material for sheets andfilms, and is useful for food packaging containers and further forcommodity packaging and laminate sheets and films, by virtue of itsexcellent transparency, impact resistance and low temperaturecharacteristics.

1. A linear block copolymer composition comprising from 55 to 95 mass %of a vinyl aromatic hydrocarbon and from 5 to 45 mass % of a conjugateddiene as monomer units, characterized in that the linear block copolymeris a mixture of a linear block copolymer having at least three types ofpolymer blocks with different molecular weights, each comprising a vinylaromatic hydrocarbon as monomer units and represented by the followingformula:S—B—S (wherein S is a polymer block comprising a vinyl aromatichydrocarbon as monomer units, and B is a polymer block comprising aconjugated diene as monomer units) and further, (1) the molecular weightdistribution (Mw/Mn) of a mixture of the polymer blocks each comprisinga vinyl aromatic hydrocarbon as monomer units, is within a range of from3.35 to 6, and (2) in a gel permeation chromatogram of a mixture of thepolymer blocks each comprising a vinyl aromatic hydrocarbon as monomerunits, M1/M2 is within a range of from 12.5 to 25, where M1 is the peaktop molecular weight corresponding to a peak at which the peak topmolecular weight becomes maximum among peaks forming a proportion of thearea of at least 30% to the whole peak area, and M2 is the peak topmolecular weight corresponding to a peak at which the peak top molecularweight becomes minimum among peaks at which the peak top molecularweight is at most 50,000 and which form a proportion of the area of atleast 20% to the whole peak area.
 2. The linear block copolymercomposition according to claim 1, wherein in a gel permeationchromatogram of a mixture of the polymer blocks each comprising a vinylaromatic hydrocarbon as monomer units, the proportion of the number ofmoles of S1 to the sum of the numbers of moles of S1 and S2 is within arange of from 5 to 25 mol %, where S1 is a component corresponding to apeak at which the peak top molecular weight becomes maximum among peaksforming a proportion of the area of at least 30% to the whole peak area,and S2 is a component corresponding to a peak at which the peak topmolecular weight becomes minimum among peaks at which the peak topmolecular weight is at most 50,000 and which form a proportion of thearea of at least 20% to the whole peak area.
 3. The linear blockcopolymer composition according to claim 1 or 2, wherein the peak topmolecular weight M2 is within a range of from 4,500 to 20,000.
 4. Thelinear block copolymer composition according to any one of claims 1 to3, wherein the peak top molecular weight M1 is within a range of from90,000 to 200,000.
 5. The linear block copolymer composition accordingto any one of claims 1 to 4, wherein in a gel permeation chromatogram ofthe linear block copolymer composition, the molecular weightdistribution (Mw/Mn) of a component corresponding to a peak at which thepeak top molecular weight becomes maximum among peaks forming aproportion of the area of at least 30% to the whole peak area, is lessthan 1.03.
 6. The linear block copolymer composition according to anyone of claims 1 to 5, wherein in a gel permeation chromatogram of thelinear block copolymer composition, M3/M4 is within a range of from 2.5to 4.5, where M3 is the peak top molecular weight corresponding to apeak at which the peak top molecular weight becomes maximum among peaksforming a proportion of the area of at least 30% to the whole peak area,and M4 is the peak top molecular weight corresponding to a peak at whichthe peak top molecular weight becomes minimum among peaks forming aproportion of the area of at least 15% to the whole peak area.
 7. Thelinear block copolymer composition according to any one of claims 1 to6, wherein in a gel permeation chromatogram of the linear blockcopolymer composition, the peak top molecular weight of a componentwhich provides the maximum peak area is within a range of from 120,000to 250,000.
 8. A composition comprising the linear block copolymercomposition as defined in any one of claims 1 to 7 and a thermoplasticresin other than the linear block copolymer composition.
 9. Thecomposition according to claim 8, wherein the mass ratio of the linearblock copolymer composition/the thermoplastic resin is from 30/70 to70/30.
 10. The composition according to claim 8 or 9, wherein thethermoplastic resin is a polystyrene polymer.